The game, postponed from the start of the season, offered Atletico the chance to peel further away from nearest challengers Real Madrid but a second draw in three games only moved them on to 55 points.
Barca, chasing a third consecutive Spanish title, are on 76 points after 35 games while Real Madrid are top with 77 and can restore their four-point advantage when they host Alaves on Friday.
La Liga has yet to officially confirm a date on which it will resume, although its president Javier Tebas had said previously he hoped the season could do so from June 12.
Real were smarting from a surprise 1-1 draw at struggling Elche in their last match and were missing captain Sergio Ramos, who was out with a stomach bug.
Morata, who had scored his first goal for the club in last week's 2-0 win over Villarreal, rose to head home from close range on the half-hour mark following a corner which had been flicked on by Atleti captain Diego Godin.
LaLiga leaders Real Madrid's pursuit of a record-extending 36th Spanish title
Images from La Liga matches played on Monday.
Barca finished the season second in the standings on 82 points, four behind champions Real Madrid who visit Leganes later on Sunday. Alaves are 16th on 39.
Roundup of the matches being held across major football leagues in Europe
A Dani Carvajal strike in the ninth-minute of stoppage time rescued Real Madrid, earning them a 3-2 comeback win at home against bottom side Almeria on Sunday in a frantic LaLiga tussle that was marked by VAR controversy.
Piotr Zielinski converted two penalties for Inter Milan as they played out a thrilling 4-4 draw with Juventus.
Here are five talking points from the weekend in La Liga:
Dada present at event bringing La Liga to India.
Real Madrid's appeal against a yellow card shown to forward Cristiano Ronaldo in Wednesday's 2-0 La Liga win at Rayo Vallecano has been granted by the Spanish soccer federation (RFEF), the club said on Friday.
The league said last week that the deal, called 'Boost La Liga', would strengthen its clubs and give them funds to spend on new infrastructure and modernisation projects as well as increasing how much they could spend on players' salaries.
Real also have an outstanding defence, conceding only 25 times last year, and are well covered in every position.
La Liga leaders Barcelona moved 10 points clear with a 4-1 win at Real Betis on Sunday after second place Atletico Madrid slipped up at Athletic Bilbao on Saturday in a 2-0 defeat.
Barcelona head into Saturday's 'Clasico' against Real Madrid with a whopping 11-point gap over their bitter rivals in the Liga title race -- and they also have the advantage in financial terms, albeit by smaller margins.
Real Madrid showed their character by beating Barcelona 2-0 in Sunday's top-of-the-table 'Clasico', leapfrogging their rivals at the La Liga summit after a week in which their pride had taken a beating at home and in Europe. Brazilian teenager Vinicius Jr scored the opener in the 71st minute with a strike that deflected off Gerard Pique, flummoxing goalkeeper Marc-Andre ter Stegen who had made some jaw-dropping saves, and substitute Mariano added the second in added time.
'But I think it is time. I'm not driven by financial matters, but by my heart. I think it's the best thing for the club. I don't want to be a problem for the club in my heart.'
Rampant Eibar humiliated European champions Real Madrid with an emphatic 3-0 win in La Liga on Saturday.
IMAGES from the UEFA Champions League matches played on Wednesday
Barcelona striker Robert Lewandowski scored twice to set his side on course for a 5-0 Champions League thrashing of Swiss side Young Boys on Tuesday as the Catalan giants bounced back from a 2-1 loss at AS Monaco in their opener.
Lionel Messi and his Barcelona team mates have been back at the club's training ground conducting individual sessions since last week, following La Liga's four-phase protocol for returning to activity since it was halted in March due to the pandemic.
Girona reclaimed top spot in LaLiga after beating champions Barcelona 4-2
Champions Barcelona lost 2-0 at Celta Vigo while Getafe earned an important 2-0 win over Girona in their bid to secure Champions League qualification.
None of Europe's top five leagues have been able to hold matches with spectators since football has returned, although championships in countries such as Serbia, Bulgaria and Denmark have allowed fans back in to matches.
Barcelona's inconsistency over the season had cost them the La Liga title, coach Luis Enrique has said.
Images from La Liga matches played on Sunday
Barcelona have appointed former German national team and Bayern Munich manager Hansi Flick as head coach on a two-year contract, the LaLiga club said on Wednesday.
After an almighty push by all parties concerned, Spain's La Liga roars back into action next week after a three-month pause due to the COVID-19 pandemic, with matches taking place every day and with everything to play for. The season resumes on Wednesday in bizarre circumstances with the second half of a Segunda Division match between Rayo Vallecano and Albacete that was abandoned in December due to offensive chanting.
Metz draw at Marseille to end losing streak
Barca, who were without injured talisman Lionel Messi, started on the back foot and fell behind when Nabil Fekir netted with a sublime angled strike in the 15th minute. Griezmann, who joined Barca last month from rivals Atletico Madrid, scored four minutes before halftime to level the scores.
A stoppage time header by fullback Lucas Vazquez earned 10-man Real Madrid a 1-0 victory at lowly Alaves.
Teenage Norway midfielder Martin Odegaard became Real Madrid's youngest La Liga debutant at the age of 16 when he came on as a substitute in the 58th minute of Saturday's final game of the season at home to Getafe.
Real Madrid's consistency and hard work made them worthy La Liga champions, captain Sergio Ramos said after their 2-0 win at Malaga on Sunday ended a five-year wait for the title.
Barcelona beat Girona 2-0 in a Catalan derby on Sunday to maintain their five-point lead at the top of La Liga, while Real Madrid thrashed Espanyol 4-2.
Karim Benzema made history at Real Madrid, the battle for the top four continues to heat up
La Liga leaders Barcelona drew 0-0 at Huesca on Saturday and are nine points clear of second-placed Atletico Madrid, who cut the gap by beating Celta Vigo 2-0.
Atletico Madrid secured a hard-fought 2-1 home victory over Real Betis in La Liga on Sunday thanks to an own-goal by Rui Silva and a header by Alvaro Morata as Diego Simeone's side ended a three-game winless run in all competitions.
