A GIANT CAKE TO THE FACE, BABY!!!

Dak's offensive lineman, La'el Collins, appeared to orchestrate the whole thing after 'Boys practice in Oxnard, Calif. ... and it was all funny as hell.

Check out the footage shot by the team ... Collins brought out a cake, and got everyone in attendance to start singing "Happy Birthday" to Dallas' big star.

They eventually coaxed the quarterback to take the cake out of its box ... and as he was admiring his birthday dessert -- Collins, Ezekiel Elliott and a bunch of other Dallas O-lineman shoved it right into his grill!!

The yellow frosting got everywhere ... in Dak's eyes, mouth and even ears!!

To his credit, Prescott took it all in stride ... though he did make sure his best buddy Elliott got a little cake in the face too!!

Overall, it was a pretty solid B-day for Dallas' signal-caller ... his girlfriend, Natalie Buffett, wished him "Happy Birthday" earlier Thursday with an adorable message.

Prescott also found out earlier in the day his shoulder injury isn't expected to be serious ... and he's slated to be ready to go for Cowboys regular season in September.