As you have mentioned, ANOVA only accepts an input of type Linear Model which can be constructed using 'fitlm' or 'stepwiselm'. If you already have the coefficients of your linear model, you can use them to generate data for the dependent variable given your independent variable values. As an example:
x = rand(1,10);
y = 5*x+12;
lm = fitlm(x,y);
Now 'lm' is a Linear Model object that will estimate the coefficients '5,12'. Given enough number of samples, 'fitlm' will estimate your model and create Linear Model object that you can then input to ANOVA.
I hope this helps,