Without hitting top gear, United doubled their advantage in the 35th after the industrious Ashley Young delivered a ideal cross from the left for Fellaini to sweep home at the far post.
Here, Press Association Sport assesses how Lukaku fared at Old Trafford as United thrashed Palace 4-0.
Louis van Gaal came and went before both were linked with exits when Jose Mourinho arrived.
The sequence occurred just three minutes into the Premier League matchup and led to United's first goal early in the game. He now has five goals and nine assists this season.
"All credit to Mourinho", said Soccer Saturday pundit Matt Le Tissier.
Mourinho reveals faith he has in 'happy' Fellaini
The former England manager, however, is relishing the opportunity to spend some time on the training pitch with his new players and instill some positive habits in them - some of which he saw evidence of in the defeat at Old Trafford. On the other hand, the home side will hope that this will be an easy three points as they head into the global break.
Lukaku, however, wasn't to be denied and tapped-in his seventh league goal of the season after Martial had sent a low cross across the box which was greedily lapped up by the burly Belgian. But in the meantime, the teenager continues to have an impact from his wide role.
The Eagles may be hoping fatigue plays a part with the hosts having played in Russian Federation in midweek.
Another game, another goal for Lukaku. For the hosts, Manchester United, they come into the game level on points with league leaders Manchester City, only with a marginally inferior goal difference thanks to City's demolition of Crystal Palace last week.
Rashford was involved in the goal and looked initially as if he might try to claim it as his free-kick, whipped in from the left, flew in at the far post. And like Pogba, he is a goal threat, just in a very different way than the Frenchman. Ruben Loftus-Cheek has a thigh issue that will keep him out this weekend, and James Tomkins was too sick to train, much less play.
And soon afterwards David de Gea had to beat away a goalbound effort from Bacary Sako.