To make the sauce: Whisk vegetable oil, soy sauce, gochujang, honey, lime juice, soy sauce, and red pepper flakes together in a bowl until well combined.

Preheat an outdoor grill for low heat and lightly oil the grate.

Place broccoli steaks onto hot grill, cover, and cook for 2 minutes. Flip and cook for another 2 minutes.

Flip broccoli steaks and generously brush with sauce, coating the stems well. Cook until lightly charred and beginning to soften, 5 to 7 minutes. Flip broccoli steaks and generously brush with sauce again. Cook until the stems are tender-crisp and cooked through, 5 to 7 minutes more.